The present invention relates to the field of cellular telephony, and more particularly to power consumed by the receiver portion of a transceiver used in wireless communication.
So-called third generation mobile phones, expected to become available in the near future, will consume significantly more power than current generation mobile phones because of the many additional services the third-generation mobiles will provide. Power is consumed by the transceiver of a mobile phone in both transmitting and receiving wireless signals. A mobile phone in communication with a base station (called a node B in third-generation cellular systems) uses a power control loop to adjust the transmit power of the mobile so that it is high enough, but only just high enough, for a signal from the mobile to be received essentially error-free by the base station. This is a basic requirement for any system using code division multiple access (CDMA) to maximize the capacity of the system. Also other radio systems typically use some kind of power control but the requirements are more relaxed. There is also a power control loop used to adjust the transmit power of the base station, which is the subject matter to which the present invention is directed.
The output power of the base station for each individual code channel is based on the properties of both the radio path and the receiver performance. The power control loop operates based on the measurements of received signal strength (RSS) and/or estimate for the signal-to-interference ratio (SIR). It is very difficult if not impossible to distinguish whether the RSS and especially SIR estimates are dominated by the receiver performance instead of the radio channel. In wideband code division multiple access (WCDMA), only the SIR estimate is used for steering the power control loop. Traditionally it has been assumed that the receiver parameters will have significant effect on the performance only when the received signal is close to the sensitivity of the receiver. In that case it is acceptable that they will affect the power control loop. At other signal levels, the radio path including propagation loss and fading and the other code channels at the band of interest are the only significant effects on SIR or RSS. However, when minimizing the power consumption, the receiver performance parameters will also change significantly even at relatively high signal levels. If a logic module with high precision is controlling the receiver performance and thus optimizing the power consumption, there will be a larger range of input power levels in which the receiver performance affects the SIR. The parameters of a receiver change whenever power consumption is scaled by for example adjusting supply current or supply voltage. Therefore, the power control loop will be forced to increase the transmitted power unnecessarily, which will lead to power competition in a CDMA system, reducing the available capacity. Thus, the scaling of power use in a receiver may disturb the power control loop. In order to allow an optimal receiver control algorithm without violating the power control loop of the system, a method that can separate a power control loop from internal control of various parameters in the receiver is required.
Accordingly, a first aspect of the invention provides a method for use by a transceiver of a first device communicating over a wireless communication system with a second device, the method characterized in that it comprises: upon a receiver portion of the transceiver of the first device completing making measurements needed for power control, transitioning the receiver portion from a power control measurement mode for making at least one predetermined power control measurement, in which at least one power control measurement is made for power control of either the first device or the second device, to an adaptive tuning mode, in which the receiver portion adapts to current conditions and so is tuned to an adaptively selected internal state; and upon the receiver portion of the first device being again scheduled to make measurements needed for power control, transitioning the receiver portion of the transceiver of the first device from the adaptive tuning mode, and so from the adaptively selected internal state, to the power control measurement mode.
A second aspect of the invention provides a method for use by a receiver of a first transceiver communicating over a wireless communication system with a second transceiver, the first transceiver having an operating cycle including an interval in which the first transceiver sends transmit power requests to the second transceiver for controlling the transmit power of the second transceiver, the transmit power requests being made based on measurements of the signal received by the first transceiver and performed in an interval of the operating cycle in which the operational parameters of the receiver are set to predetermined measurement mode values defining a power control measurement state, the method characterized in that it comprises: a step of waiting for an interval of the operating cycle of the receiver in which no measurements for power control are scheduled and then enabling receiver tuning to adjust the operational parameters of the receiver to place the receiver in an internal state; a step of disabling receiver tuning when measurements for power control are again scheduled; and a step of placing the receiver back into the power control measurement state.
In further accord with the second aspect of the invention, the method is further characterized in that, before enabling receiver tuning, the receiver is placed in the internal state to which the receiver was tuned during the previous duty cycle.
A third aspect of the invention provides an apparatus for use by a transceiver of a first device communicating over a wireless communication system with a second device, characterized in that it comprises: means for transitioning the receiver portion from a predetermined power control measurement mode, in which measurements are made for power control of either the first device or the second device, to an adaptive tuning mode, in which the receiver adapts to current conditions and so is tuned to an adaptively selected internal state, the transitioning being triggered by the receiver portion of the transceiver of the first device completing a set of measurements needed for power control; and means for transitioning the receiver portion of the transceiver of the first device from the adaptive tuning mode to the power control measurement mode when the receiver of the first device is again scheduled to make measurements needed for power control.
A fourth aspect of the invention provides an apparatus for use with a receiver of a first transceiver communicating over a wireless communication system with a second transceiver, the first transceiver having an operating cycle including an interval in which the first transceiver sends transmit power requests to the second transceiver for controlling the transmit power of the second transceiver, the transmit power requests being made based on measurements of the signal received by the first transceiver and performed in an interval of the operating cycle in which the operational parameters of the receiver are set to predetermined measurement mode values defining a power control measurement state, the apparatus characterized in that it comprises: control mode logic for waiting for an interval of the operating cycle of the receiver in which no measurements for power control are scheduled, responsive to a synchronization signal indicating information about timing of received data, and further responsive to system state information indicating information about timing for making power control measurements, for providing enable and disable tuning commands; and receiver tuning logic, responsive to the enable and disable tuning commands, for providing tuning commands adjusting operational parameters of the receiver so as to place the receiver in an internal state adapted to existing operating conditions.
In further accord with the fourth aspect of the invention, the apparatus is further characterized in that in response to an enable tuning command, the tuning commands issued by the receiver tuning logic place the receiver in the internal state to which the receiver was tuned during the previous duty cycle.
Thus, in the present invention, a method that can separate a power control loop from internal control of various parameters in the receiver is provided by dividing the reception in time into two periods. The system measurements can be performed during one time slot at fixed predetermined conditions and the rest of the time can be used for internal control of the receiver. The required time to do the system measurements can be short compared to the measurement period without significantly deteriorating the accuracy of the required measurements. Hence, most of the time it is possible to control the receiver parameters without strict limitations to minimize the power consumption. The invention permits having an adaptively tunable receiver in continuous reception without violating the power control loop of a CDMA system or any other radio system that uses a similar kind of power control loop.
Although the invention relates primarily to the control of a mobile cellular receiver with respect to power consumption, it is possible to use the invention also in other portable radio receivers or even in a base station using a power control loop. The optimized functionality in the receiver need not be only with respect to power consumption; the receiver performance can also be optimized according to the invention based on some other parameter, such as a noise figure.